In industrial settings such as plants, factories, or other large-scale systems that utilize three-phase power, switching power supplies and variable frequency drives, harmonic noise present in three-phase circuits can cause numerous problems. Harmonic noise can destroy electronic components, increase the number of control lock-ups requiring rebooting, shorten the life of electric motors, and lower system reliability.
These harmonics may be caused by switching occurring at an upstream power-station, switch mode power supplies and variable frequency drives, or numerous other events. Such harmonics can severely damage or destroy equipment connected to the affected three-phase circuit, or, when the system employs circuit interrupters, can cause those interrupters to open the circuit, resulting in power outages throughout the plant. Such outages have negative economic effects since productive equipment remains non-functional until the circuit is re-energized.
Inductors have been used for harmonic mitigation for many years. However, the prior art systems have several shortcomings. Variable frequency drives generate more noise when running with a light load, and inductors, which are current smoothing devices, are ineffective at removing electrical noise including harmonics. Such a system causes stress on devices connected to the circuit and may damage or cause permanent failure of the components. Additionally, the solid-state components used in the drive systems are degraded by the harmonics caused by the drive itself.